Structural phase evolution of strontium-doped lead titanate thin films prepared by the soft chemical technique

Strontium-modified lead titanate thin films with composition Pb1-xSrxTiO3 were grown on Pt/Ti/SiO2/Si substrates using the polymeric precursor method. The structural phase evolution as a function of the Sr contents was studied using micro-Raman scattering, specular reflectance infrared Fourier transform spectroscopy, and x-ray diffraction. The results showed a gradual change from tetragonal to cubic structure, the transition occurring at about x = 0.58. The infrared reflectance spectra showed that the frequency of several peaks decreases as the strontium concentration increases. These features are correlated with a decrease in the tetragonal distortion of the TiO6 octahedra as the strontium concentration increases.

Extração de matéria orgânica aquática por abaixamento de temperatura: Uma metodologia alternativa para manter a identidade da amostra

In this work was developed an alternative methodology to separation of aquatic organic matter (AOM) present in natural river waters. The process is based in temperature decreasing of the aqueous sample under controlled conditions that provoke the freezing of the sample and separation of the dark extract, not frozen and rich in organic matter. The results showed that speed of temperature decreasing exerts strongly influence in relative recovery of organic carbon, enrichment and time separation of the organic matter present in water samples. Elemental composition, infrared spectra and thermal analysis results showed that the alternative methodology is less aggressive possible in the attempt of maintaining the integrity of the sample.

A thermal behaviour study of solid-state cinnamates of the latter trivalent lanthanides and yttrium(III)

Some new compounds of cinnamic acid with the latter trivalent lanthanides and yttrium(III) were synthesized in the solid state. The compounds have the general formula LnL3, where Ln represents trivalent Eu to Lu or Y ions and L is the cinnamate anion (C6H5-CH=CH-COO-). Thermogravimetry (TG), derivative thermogravimetry (DTG), differential scanning calorimetry (DSC), infrared absorption spectra and X-ray diffraction powder patterns were used to characterize and to study the thermal behaviour of these compounds. © 2002 Elsevier Science B.V. All rights reserved.

Dental implants: Surface modification of cp-Ti using plasma spraying and the deposition of hydroxyapatite

The commercial pure titanium (cp-Ti) is currently being used with great success in dental implants. In this work we investigate how the cp-Ti implants can be improved by modifying the metal surface morphology, on which a synthetic material with properties similar to that of the inorganic part of the bone, is deposited to facilitate the bone/implant bonding. This synthetic material is the hydroxyapatite, HA, a calcium-phosphate ceramic. The surface modification consists in the application of a titanium oxide (TiO2) layer, using the thermal aspersion - plasma spray technique, with posterior deposition of HA, using the biomimetic method. The X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray (EDX) and Diffuse Reflectance Infrared Fourier Transform (DRIFT) techniques have been used for characterizing phases, microstructures and morphologies of the coatings. The TiO2 deposit shows a mixture of anatase, rutilo and TiO2-x phases, and a porous and laminar morphology, which facilitate the HA deposition. After the thermal treatment, the previously amorphous structured HA coating, shows a porous homogeneous morphology with particle size of about 2-2.5 μm, with crystallinity and composition similar to that of the biological HA.

Spectroscopic studies of SnO2 doped with Cr, Co or Nb

SnO2 ceramics doped with different amounts of Co, Cr or Nb were investigated using visible and infrared spectroscopy at room temperature. Based on the observed d-d transitions the valence states of incorporated dopants were determined. Values of the optical band-gap were calculated in all samples. The infrared spectra of the samples displayed variations in the position, relative intensity and width of the bands, which were attributed to the presence of dopants.

Thermal Behavior and Spectroscopic Study of Neutral and Cationic Mononuclear Cyclopalladated Compounds

The reactions of the precursor [Pd(N,C-dmba)(MeCN)2](NO 3) (1) (dmba = N,N-dimethylbenzylamine), with the proligands 3,5-dimethylpyrazole (Hdmpz), 2-quinolinethiol (qnSH) and 1,1′- bis(diphenylphosphine)ferrocene (dppf) afforded the compounds [Pd(N,C-dmba)(Hdmpz)(ONO2)]0.5CH2Cl2 (2), [Pd(N,C-dmba)(qnSH)(ONO2)] 0.5CH2Cl2 (3) and [Pd(N,C-dmba)(dppf)](NO3) (4), respectively. The mononuclear species 2,3 and 4 were characterized by elemental analysis, infrared spectroscopy, NMR and thermogravimetric analysis. The IR spectra show bands which are consistent with terminal monodentate nitrate group for 2-3 and ionic nitrate for 4. The 1H and 13C NMR data confirm that coordination of the organic ligands has occurred and the 31P{1H} NMR data for 4 clearly evidences the occurrence in solution of three cyclopalladated species with the dppf acting as a bridging ligand in two cases and as a chelate in one. The thermal behavior of compounds 1-4 suggests that complex 2 is the most stable. The X-ray diffractometry results show the formation of PdO from 1 and 2, Pd2OSO4 from 3, and of a mixture of PdO and Fe 2(PO4)3 from 4, as final decomposition products.

Dielectric and viscoelastic properties of cross-linked polyethylene aged under multi stressing conditions

Different measurements were performed in cross-linked polyethylene (XLPE) employed as insulating material in coaxial cables that were field-aged and laboratory-aged under multi-stressing conditions at room temperature. Samples were peeled from the XLPE cable insulation in three different positions: just below the external semiconductor layer (outer layer), in the middle (middle layer) and just above the internal semiconductor layer of the cable (inner layer). The imaginary part of the electric susceptibility showed three peaks that obey the Dissado-Hill model. For laboratory-aged XLPE samples peeled from the inner and from the middle positions the peak at very low frequency region increased while in samples from the outer position a quasi-DC conduction process was observed. In medium frequency range a broadening of the peak was observed for all samples. Viscoelastic properties determined through dynamic mechanical analysis suggested that the aging generates processes that promoted changes of the crystallinity and the cross-linking degrees of the polymer. Fourier transform infrared spectroscopy (FTIR) measurements revealed an increase of oxidation products (esters), evidence of polar residues of the bow-tie tree and the presence of cross-linking by-products (acetophenone). Optical and scanning electronic microscope (SEM) measurements in aged samples revealed the existence of voids and bow-tie trees that were formed during aging in the middle region of the cable.

Synthesis and spectroscopic characterization of new metal(II) complexes with methionine sulfoxide

Methionine sulfoxide complexes of iron(II) and copper(II) were synthesized and characterized by chemical and spectroscopic techniques. Elemental and atomic absorption analyses fit the compositions K2[Fe(metSO) 2]SO4 · H2O and [Cu(metSO)2] · H2O. Electronic absorption spectra of the complexes are typical of octahedral geometries. Infrared spectroscopy suggests coordination of the ligand to the metal through the carboxylate and sulfoxide groups. An EPR spectrum of the Cu(II) complex indicates tetragonal distortion of its octahedral symmetry. 57Fe Mössbauer parameters are also consistent with octahedral stereochemistry for the iron(II) complex. The complexes are very soluble in water.

Synthesis and characterization of poly-o-toluidine: Kinetic and structural aspects

Poly(o-methylaniline) (poly-o-toluidine, PTOL) was synthesized by chemical oxidation of o-toluidine with ammonium peroxydisulfate in an aqueous 1.0 mol L -1 HCl solution. The progress of polymerization was followed by measuring the open-circuit potential (OCP) of a Pt electrode immersed in the reaction medium with the polymerization time. The chemical synthesis of PTOL was carried out at different monomer:oxidant (M:O) molar ratios (4:1, 2:1, 1.5:1, 1:1, and 0.66:1), and the products obtained were characterized by infrared spectroscopy, gel permeation chromatography, and X-ray diffraction. The molecular weight and percentage of crystallinity of PTOL are higher for samples synthesized in an excess of the monomer, i.e. at higher M:O ratios. However, the yield of PTOL prepared at higher M:O ratios is considerably low, in particular at a 4:1 M:O ratio, which is the M:O ratio most commonly used in the literature to synthesize polyaniline and its derivatives.

Synthesis, characterization, and biological activity of a new palladium(II) complex with deoxyalliin

Synthesis, characterization, and biological activity of a new water-soluble Pd(II)-deoxyalliin (S-allyl-L-cysteine) complex are described in this article. Elemental and thermal analysis for the complex are consistent with the formula [Pd(C6H10NO2S)2]. 13C NMR, 1H NMR, and IR spectroscopy show coordination of the ligand to Pd(II) through S and N atoms in a square planar geometry. Final residue of the thermal treatment was identified as a mixture of PdO and metallic Pd. Antiproliferative assays using aqueous solutions of the complex against HeLa and TM5 tumor cells showed a pronounced activity of the complex even at low concentrations. After incubation for 24 h, the complex induced cytotoxic effect over HeLa cells when used at concentrations higher than 0.40 mmol/L. At lower concentrations, the complex was nontoxic, indicating its action is probably due to cell cycle arrest, rather than cell death. In agreement with these results, the flow cytometric analysis indicated that after incubation for 24 h at low concentrations of the complex cells are arrested in G0/G1. © 2005 NRC Canada.

Synthesis, characterization and thermal behaviour of solid-state compounds of 4-methoxybenzoate with some bivalent transition metal ions

Solid-state M-4-MeO-Bz compounds, where M stands for bivalent Mn, Co, Ni, Cu and Zn and 4-MeO-Bz is 4-methoxybenzoate, have been synthesized. Simultaneous thermogravimetry-differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), X-ray powder diffractometry, infrared spectroscopy, elemental analysis and complexometry were used to characterize and to study the thermal behaviour of these compounds. The results led to have information about the composition, dehydration, thermal stability and thermal decomposition of the isolated compounds. © 2005 Akadémiai Kiadó, Budapest.

Mechanism of the formation and properties of antimony polyphosphate

Formation of antimony polyphosphate using Sb2O3 and/or (NH4)2HPO4 and NH4H 2PO4 as starting materials has been simulated by thermal analysis technique. The elimination of water and ammonia molecules induced by heating leads to the formation of intermediate ammonium polyphosphate, which subsequently reacts with Sb2O3. Morphologically, vitreous Sb(PO3)3 is composed of plaques having irregular shapes. Infrared spectra and NMR study is consistent with tetrametaphosphate anion arrangement. The compound is thermally unstable and may be recommended as a donor of -O-P-O- linkers in the preparation of special phosphate glasses. © 2005 Akadémiai Kiadó, Budapest.

Four new metal complexes with the amino acid deoxyalliin

The solid complexes [Co(C6H10NO2S) 2], [Ni(C6H10NO2S)2], [Cu(C6H10NO2S)2] and [Fe(C 6H10NO2S)2] were obtained from the reaction of cobalt(II), nickel(II), copper(II) and iron(II) salts with the potassium salt of the amino acid deoxyalliin (S-allyl-L-cysteine). Electronic absorption spectra of the complexes are typical of octahedral structures. Infrared spectroscopy confirms the ligand coordination to the metal ions through (COO-) and (NH2) groups. EPR spectrum of the Cu(II) complex indicates a slight distortion of its octahedral symmetry. Mössbauer parameters permitted to identify the presence of iron(II) and iron(III) species in the same sample, both of octahedral geometry. Thermal decomposition of the complexes lead to the formation of CoO, NiO, CuO and Fe2O3 as final products. The compounds show poor solubility in water and in the common organic solvents. ©2005 Sociedade Brasileira de Química.

Effect of lithium doping on the evolution of rheological and structural properties during gelation of siloxane-poly(oxypropylene) nanocomposites

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

2,3,4,6-Tetra-O-(3-nitropropanoyl)-O-β-D-glucopyranoside, a new antimicrobial from the roots of Heteropteris aphrodisiaca

A new 2,3,4,6-tetra-O-(3-nitropropanoyl)-O-β-D-glucopyranoside anomer was isolated from the roots of Heteropteris aphrodisiaca and characterized by spectroscopic methods. Activity against Staphylococcus aureus, Bacillus subtilis, Candida albicans, C. parapsilosis, C. krusei, and C. tropicalis was demonstrated.